As apparatuses for manufacturing a metal plate by hot-rolling-treating scrap material (a metal material) mainly composed of steel and including copper, hot rolling apparatuses are conventionally used in which a heat-treated metal material is thinned through a plurality of hot rolling operations by a rolling mill.
Some of such hot rolling apparatuses have a construction in which there is arranged in a line: a roughing mill for rolling the metal material heat-treated to an elevated temperature a plurality of times while passing the metal material back and forth, to thereby mold the metal material into a metal plate; a heat-retention chamber for, for example, keeping the metal plate molded by the roughing mill at temperatures lower than that in the heating treatment; a finishing mill train for finish-rolling the metal plate that has been carried out of the heat-retention chamber; and a cooling apparatus for cooling the metal plate that has been carried out of the finishing mill train.
For example, Patent Document 1 discloses a hot rolling apparatus in which a coil box that stores the metal plate molded by the roughing mill in a predetermined temperature atmosphere after coiling is placed as the heat-retention chamber. According to the hot rolling apparatus disclosed in Patent Document 1, a metal plate is coiled in the coil box. Therefore, it is possible to realize a hot rolling apparatus with a reduced line length.
Patent Document 2 discloses a hot rolling apparatus that rolls a metal material simultaneously with a roughing mill and a finishing mill train. According to the hot rolling apparatus disclosed in Patent Document 2, it is possible to realize a compact hot rolling apparatus in which a metal material is continuously processed with a roughing mill and a finishing mill train.    Patent Document 1: Unexamined Japanese Patent Application, First Publication No. S48-62651    Patent Document 2: Japanese Patent No. 3146786